An aneurysm is a type of disease that affects the arteries and is manifested by a localized widening or enlargement of an artery compared to its normal size. Because of the potential of rupture of the artery in question, any aneurysm is a serious health problem and risk to a patient. When a blood vessel with an aneurysm ruptures, life-threatening bleeding generally is the result. Even prior to such an occurrence, aneurysms can also cause pain from pressure on nearby organs or nerves and on occasion, debris within the aneurysm can dislodge and thereafter be communicated through the circulatory system of the patient to the legs or vital organs. The result is generally a blocking of the blood flow to these tissues and resulting harm to organs and tissues remote to the aneurysm itself.
A common location for aneurysms is in the abdominal aorta, which is one of the largest blood vessels in the body and located in the abdominal region of the body. A rupture of such a large blood vessel has dire and life threatening consequences to the individual suffering such a crisis. Such abdominal aortic aneurysms (AAA's) most often involve the infrarenal aorta which is the portion of the blood vessel that lies below the takeoff of the arteries to the kidneys (renal arteries). About half of AAA's also involve the iliac arteries in the pelvis. The major risk associated with AAA's is that they have a high propensity to rupture and currently such ruptures are the 13th leading cause of death in the United States. Therefore, early detection and timely repair are paramount to the patient.
Current medical practice which is least invasive to the patient employs endovascular repair or stent grafting, in a procedure which is performed through small incisions in each groin. While carrying many of the same risks as invasive surgical repair, patients usually spend fewer days in the hospital and recover more quickly with less pain with the implantation of an endovascular prosthesis.
In a procedure to implant the prosthesis, a bifurcated stent graft is positioned within the aneurysm to provide a new conduit for blood flow through the damaged portion of the blood vessel. This effectively seals off the diseased and bulging portion of the aorta from the blood flow and eliminates the potential for rupture.
A common endoprosthesis for repair of an AAA is a two-piece bifurcated endovascular graft which is positioned to line the aorta within the aneurysm and has a first portion adapted to engage within the aorta, which communicates with two graft conduits, and which extends from below the renal arteries into both iliac arteries. Material such as ePTFE (expanded polytetrafluoroethylene) forming this fluid conduit for blood flow is commonly inert when implanted. A structural metallic component known generally as a stent is engaged in a skeletal arrangement with the material to maintain the formed conduits for blood flow in an expanded condition once implanted.
Delivery and implantation of the device to the site of the aneurysm in the abdominal aorta is generally done by assembly of two component sections which include the trunk with a cuff adapted to engage the contralateral leg. The trunk portion has a large diameter adapted to engage within the large internal diameter of the aorta and is implanted to a position just below the renal arteries. Extending from the trunk and having an internal conduit in communication with the internal passage of the trunk portion is the ipsilateral leg which is positioned in communication within one of the iliac arteries when deployed. The trunk and first leg are conventionally formed and deployed as a unitary structure. The cuff also extends from the trunk portion and, as noted, is adapted for engagement to the second leg which is positioned once engaged within a second of the iliac arteries. The engagement of the contralateral leg with the cuff and positioning of its distal end within the other of the iliac arteries completes the stent graft.
This two-piece construction yields is required because of the nature of the engagement of the two legs from the trunk into two different iliac arteries. However, assembly of these two components inside the body of the patient during surgery can be a vexing task to even the most experienced and knowledgeable surgeon. This is because the visual display depicting the components during assembly is a two-dimensional video visualization of a three-dimensional communication between the components of the implant and the two iliac arteries in their junction to the aorta. These arteries generally engage with the aorta at angles radial to the axis of the aorta which must be accommodated during the engagement of the contralateral leg portion with the short extending cuff from the trunk portion.
Currently, the trunk portion and first leg portion are advanced using a catheter and guide wire through an incision in one of the femoral arteries. Once inserted into a femoral artery, the trunk and extending first leg and cuff are advanced over the guide wire to the proper position at the juncture of the aorta and renal arteries. During this translation into the aneurysm, the trunk, cuff, and ipsilateral leg are held in a compressed state at the distal end of the catheter by a restraining mechanism which can at a chosen time be released by controls positioned outside the patient's body to allow the stent graft to enlarge to its expanded state, thereby engaging within the vessel at the appropriate point. Once proper positioning is determined by the surgeon using radiopaque markers and fluoroscopic visualization of the distal end of the first catheter, a control mechanism communicating with the restraining mechanism is activated. This allows for enlargement of the trunk and first leg in their respective positions in the aorta and iliac artery.
It is at this point in the procedure that the surgery can become uncertain as to duration and an ongoing source of frustration to the surgeon. Attachment of the second or contralateral leg to the distal end of the cuff portion extending from the trunk is achieved by translating a guide wire from the second leg artery which must be visually guided into the aperture at the distal end of the cuff extending from the trunk. Once so positioned, the contralateral leg may be translated over the guide wire and into proper position relative to the cuff and enlarged to engage the contralateral leg to the cuff.
While this may sound like a simple procedure in principle, in practice it is both frustrating and can be extremely time consuming. The extra time in the operating room and uncertainty as to operation duration impacts the surgery schedules for subsequent surgeries. Additionally, during this engagement process of the contralateral leg to the cuff, the patient remains under anesthesia, exposed to continual x-ray radiation, and subjected to continued manipulation of the guide wire inside the vessel adjacent to the cuff. Since there is usually extensive clot and atherosclerotic plaque within the aneurysm, such manipulation entails the additional risk of dislodging debris within the lumen of the aneurysm, thereby also raising the risk of such debris traveling to branch arteries of the aorta.
The primary problem in this engagement step arises from the wide variance of intersecting angles of the radially extending iliac arteries from the aorta. The resulting angles of the graft legs may be highly divergent from the axis of the trunk. However, in the two-dimensional visualization provided by the fluoroscope, the surgeon is visually hindered in the attempt to thread the guide wire into the aperture at the distal end of the cuff. An additional factor complicating wire passage into the cuff is that the cuff is usually near the center of the large cavity formed by the aneurysm which in many cases can exceed 10 cm in diameter. The engagement of a small diameter cuff positioned in the midst of such a comparatively large space with the aid of only two-dimensional imaging, while concurrently contending with the highly variable angles of approach from the iliac arteries, renders the procedure very unpredictable.
Further, in many cases the angles leading to the iliac arteries from the aorta are such that the surgeon will choose to cross over the first leg and contralateral leg in an overlapping arrangement to maintain a continuous curve for blood flow and to avoid kinks. When graft legs are crossed, attempts at passage of a wire from the second iliac artery into the cuff may additionally be complicated by interference from the first leg which, when positioned in the cross-leg deployment format, will lie across the opening from the second iliac artery into the aorta. Even highly trained surgeons with years of experience can become bogged down trying to thread the guide wire into the aperture of the cuff using the two dimensional visualization and overlapping of images available on the fluoroscopic screen. Absent a lucky positioning of the guide wire, such an exercise can consume an inordinate amount of time.
As such, there exists an unmet need for a bifurcated endoprosthesis which can be more easily assembled from components to repair aortic aneurysms. Such a device should allow for conventional deployment of the trunk portion and first extending leg and cuff in a relatively conventional fashion to facilitate easy adoption of the device and procedure. However, such a device and method should provide a means to eliminate the frustration and time-consuming step requiring the surgeon to fish with the distal end of a second guide wire for the aperture of the cuff extending from the trunk portion. In this fashion implantation surgeries for such devices may be expedited and performed with a reasonably accurate estimate of duration, and patients undergoing such surgeries will benefit from shortened procedures and be spared exposure to prolonged radiation.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangement of the components set forth in the following description or illustrated in the drawings nor the steps outlined in the specification. The invention is capable of other embodiments and of being practiced and carried out in various ways as those skilled in the art will readily ascertain from reading this application. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other methods and systems for carrying out the several purposes of the present invention of a device and method for implanting a bifurcated prosthesis in an aortic aneurysm. It is important, therefore, that the claims be regarded as including such equivalent construction insofar as they do not depart from the spirit and scope of the present invention.